The present invention relates to intumescent compositions based on foamed or unfoamed polyurethanes and containing aromatic hydroxy carboxylic acids as part of the formulation.
Intumescent compositions are generally understood to be compositions which foam under the effect of fire and heat and form an insulating and fire-resistant foam which protects the zones situated behind the foam against fire. Such intumescent compositions are generally known in the form of lacquers, coatings and mortars or cements.
In order to be particularly useful, an intumescent composition must combine various properties. For example, it must foam above 100.degree. C. and below 300.degree. C., and preferably between 200.degree. and 300.degree. C. Secondly, it must foam both in the event of direct contact with the flame (i.e., in the event of rapid heating) and also when the foaming temperature is reached very slowly (e.g., over a period of as long as one hour, such as generally is the case for a smouldering fire). The intumescent composition heated very slowly to its foaming temperature should still be capable of foaming when it comes into contact with a flame. Furthermore, in the event of slow or rapid heating, little or no shrinkage should occur, and, such shrinkage as may occur, should be overcompensated for above the foaming temperature. Intumescent compositions whose effectiveness is not impaired by the presence of water would also be particularly advantageous. Additionally, it would also be as advantageous if the intumescent composition showed very good thermal insulation, even in the absence of thermal stressing. Finally, intumescent compositions must be free from halogen (risk of corrosion).
Although conventional intumescent compositions satisfy some of the requirements mentioned above, there is no known intumescent composition which satisfies all these requirements.
Accordingly, there is a need for improved intumescent compositions of the type in question. The present invention provides such intumescent compositions.